Generating Combinations Quiz Online Practice Test

1. What does the term "lexicographical order" refer to?

2. How many unique combinations of 2 elements can be selected from the array arr = {1, 2, 3}?

3. What is the lexicographical sequence of all 2-element combinations from the array arr = {1, 2, 3}?

4. What is the auxiliary space complexity (excluding the call stack) required by a program to generate combinations of r elements from an array of size n?

5. Is the code for generating combinations considered to be in-place?

6. What is the time complexity of the algorithm used to generate and print combinations?

7. What will be the output of the following code?

#include <stdio.h>
void combination(int arr[], int n, int r, int index, int aux[], int i);
void print(int arr[], int n, int r) {
int aux[r];
combination(arr, n, r, 0, aux, 0);
}
void combination(int arr[], int n, int r, int index, int aux[], int i) {
if (index == r) {
for (int j = 0; j < r; j++)
printf("%d ", aux[j]);
printf(", ");
return;
}
if (i >= n)
return;
aux[index] = arr[i];
combination(arr, n, r, index + 1, aux, i + 1);
combination(arr, n, r, index, aux, i + 1);
}
int main() {
int arr[] = {1, 2, 2};
int r = 2;
int n = sizeof(arr) / sizeof(arr[0]);
print(arr, n, r);
return 0;
}

8. What will be the output of the following code?

#include <stdio.h>
void combination(int arr[], int aux[], int start, int end, int index, int r);
void print(int arr[], int n, int r) {
int aux[r];
combination(arr, aux, 0, n-1, 0, r);
}
void combination(int arr[], int aux[], int start, int end, int index, int r) {
if (index == r) {
for (int j = 0; j < r; j++)
printf("%d ", aux[j]);
printf(", ");
return;
}
for (int i = start; i <= end && end - i + 1 >= r - index; i++) {
aux[index] = arr[i];
combination(arr, aux, i + 1, end, index + 1, r);
}
}
int main() {
int arr[] = {1, 2, 3};
int r = 2;
int n = sizeof(arr) / sizeof(arr[0]);
print(arr, n, r);
}